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  Subjects -> ENGINEERING (Total: 2246 journals)
    - CHEMICAL ENGINEERING (188 journals)
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    - ELECTRICAL ENGINEERING (98 journals)
    - ENGINEERING (1191 journals)
    - ENGINEERING MECHANICS AND MATERIALS (386 journals)
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CHEMICAL ENGINEERING (188 journals)                     

Showing 1 - 0 of 0 Journals sorted alphabetically
AATCC Journal of Research     Full-text available via subscription   (Followers: 4)
ACS Sustainable Chemistry & Engineering     Hybrid Journal  
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 4)
Acta Polymerica     Hybrid Journal   (Followers: 7)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 6)
Advanced Chemical Engineering Research     Open Access   (Followers: 27)
Advanced Powder Technology     Hybrid Journal   (Followers: 13)
Advances in Applied Ceramics     Hybrid Journal   (Followers: 4)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 23)
Advances in Chemical Engineering and Science     Open Access   (Followers: 50)
Advances in Polymer Technology     Hybrid Journal   (Followers: 12)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 9)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 6)
Applied Petrochemical Research     Open Access   (Followers: 2)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 7)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 13)
Biofuel Research Journal     Open Access   (Followers: 3)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 11)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of Chemical Reaction Engineering & Catalysis     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 3)
Carbohydrate Polymers     Hybrid Journal   (Followers: 7)
Catalysts     Open Access   (Followers: 6)
ChemBioEng Reviews     Full-text available via subscription  
Chemical and Engineering News     Free   (Followers: 11)
Chemical and Materials Engineering     Open Access   (Followers: 6)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 10)
Chemical and Process Engineering     Open Access   (Followers: 20)
Chemical and Process Engineering Research     Open Access   (Followers: 18)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 33)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 17)
Chemical Engineering and Science     Open Access   (Followers: 13)
Chemical Engineering Communications     Hybrid Journal   (Followers: 12)
Chemical Engineering Journal     Hybrid Journal   (Followers: 27)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 21)
Chemical Engineering Research Bulletin     Open Access   (Followers: 8)
Chemical Engineering Science     Hybrid Journal   (Followers: 20)
Chemical Geology     Hybrid Journal   (Followers: 14)
Chemical Papers     Hybrid Journal   (Followers: 2)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 127)
Chemical Society Reviews     Full-text available via subscription   (Followers: 39)
Chemical Technology     Open Access   (Followers: 11)
ChemInform     Hybrid Journal   (Followers: 4)
Chemistry & Industry     Hybrid Journal   (Followers: 3)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry of Materials     Full-text available via subscription   (Followers: 143)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
ChemSusChem     Hybrid Journal   (Followers: 5)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal   (Followers: 1)
Coloration Technology     Hybrid Journal  
Computational Biology and Chemistry     Hybrid Journal   (Followers: 9)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 1)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
CORROSION     Full-text available via subscription   (Followers: 19)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 35)
Corrosion Reviews     Hybrid Journal   (Followers: 3)
Crystal Research and Technology     Hybrid Journal   (Followers: 5)
Current Opinion in Chemical Engineering     Open Access   (Followers: 7)
Education for Chemical Engineers     Hybrid Journal   (Followers: 4)
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription  
European Polymer Journal     Hybrid Journal   (Followers: 40)
Fibers and Polymers     Full-text available via subscription   (Followers: 4)
Fluorescent Materials     Open Access   (Followers: 1)
Focusing on Modern Food Industry     Open Access   (Followers: 2)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 1)
Gels     Open Access  
Geochemistry International     Hybrid Journal   (Followers: 2)
Handbook of Powder Technology     Full-text available via subscription   (Followers: 3)
Heat Exchangers     Open Access   (Followers: 1)
High Performance Polymers     Hybrid Journal  
Hungarian Journal of Industry and Chemistry     Open Access  
Indian Chemical Engineer     Hybrid Journal   (Followers: 5)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 9)
Indonesian Journal of Chemical Science     Open Access  
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 9)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 20)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 3)
Industrial Gases     Open Access  
Info Chimie Magazine     Full-text available via subscription   (Followers: 3)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 2)
International Journal of Chemical Engineering     Open Access   (Followers: 6)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 2)
International Journal of Chemical Technology     Open Access   (Followers: 5)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 3)
International Journal of Industrial Chemistry     Open Access  
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 5)
International Journal of Science and Engineering     Open Access   (Followers: 4)
International Journal of Waste Resources     Open Access   (Followers: 3)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 4)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 5)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 10)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 102)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 9)
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 10)
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 6)
Journal of Chemical Engineering     Open Access   (Followers: 13)
Journal of Chemical Engineering and Materials Science     Open Access   (Followers: 2)
Journal of Chemical Science and Technology     Open Access   (Followers: 4)
Journal of Chemical Sciences     Partially Free   (Followers: 17)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 10)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 15)
Journal of CO2 Utilization     Hybrid Journal   (Followers: 2)
Journal of Crystallization Process and Technology     Open Access   (Followers: 7)
Journal of Environmental Chemical Engineering     Hybrid Journal   (Followers: 3)
Journal of Food Measurement and Characterization     Hybrid Journal  
Journal of Food Processing & Technology     Open Access  
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 4)
Journal of Geochemical Exploration     Hybrid Journal   (Followers: 1)
Journal of Industrial and Engineering Chemistry     Hybrid Journal   (Followers: 1)
Journal of Information Display     Hybrid Journal  
Journal of Inorganic and Organometallic Polymers and Materials     Partially Free   (Followers: 7)
Journal of Modern Chemistry & Chemical Technology     Full-text available via subscription   (Followers: 2)
Journal of Molecular Catalysis A: Chemical     Hybrid Journal   (Followers: 5)
Journal of Non-Crystalline Solids     Hybrid Journal   (Followers: 7)
Journal of Organic Semiconductors     Open Access   (Followers: 4)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 5)
Journal of Polymer and Biopolymer Physics Chemistry     Open Access   (Followers: 4)
Journal of Polymer Engineering     Hybrid Journal   (Followers: 8)
Journal of Polymer Research     Hybrid Journal   (Followers: 6)
Journal of Polymer Science Part C : Polymer Letters     Hybrid Journal   (Followers: 5)
Journal of Polymers     Open Access   (Followers: 2)
Journal of Polymers and the Environment     Hybrid Journal   (Followers: 1)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 1)
Journal of the American Chemical Society     Full-text available via subscription   (Followers: 245)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Brazilian Chemical Society     Open Access   (Followers: 2)
Journal of The Institution of Engineers (India) : Series E     Hybrid Journal   (Followers: 1)
Journal of the Pakistan Institute of Chemical Engineers     Open Access   (Followers: 1)
Journal of the Taiwan Institute of Chemical Engineers     Hybrid Journal   (Followers: 2)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 8)
Jurnal Bahan Alam Terbarukan     Open Access  
Jurnal Inovasi Pendidikan Kimia     Open Access  
Jurnal Reaktor     Open Access  
Jurnal Teknologi Dan Industri Pangan     Open Access   (Followers: 1)
Korean Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
Main Group Metal Chemistry     Hybrid Journal   (Followers: 1)
Materials Chemistry and Physics     Full-text available via subscription   (Followers: 14)
Materials Science and Applied Chemistry     Open Access  
Materials Sciences and Applied Chemistry     Full-text available via subscription  
Modern Chemistry & Applications     Open Access  
Molecular Imprinting     Open Access  
Nanocontainers     Open Access  
Nanofabrication     Open Access  
Noise Control Engineering Journal     Full-text available via subscription   (Followers: 2)
Ochrona Srodowiska i Zasobów Naturalnych : Environmental Protection and Natural Resources     Open Access  
Petroleum Chemistry     Hybrid Journal   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 3)
Plasma Processes and Polymers     Hybrid Journal  
Plasmas and Polymers     Hybrid Journal  
Polymer     Hybrid Journal   (Followers: 104)
Polymer Bulletin     Hybrid Journal   (Followers: 7)
Polymer Composites     Hybrid Journal   (Followers: 13)
Polyolefins Journal     Open Access  
Powder Technology     Hybrid Journal   (Followers: 12)
Recyclable Catalysis     Open Access   (Followers: 1)
Research on Chemical Intermediates     Hybrid Journal  
Reviews in Chemical Engineering     Hybrid Journal   (Followers: 5)
Revista Cubana de Química     Open Access  
Revista ION     Open Access  
Revista Mexicana de Ingeniería Química     Open Access  
Rubber Chemistry and Technology     Full-text available via subscription   (Followers: 2)
Russian Chemical Bulletin     Hybrid Journal   (Followers: 2)
Russian Journal of Applied Chemistry     Hybrid Journal   (Followers: 1)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 57)
Solid Fuel Chemistry     Hybrid Journal  
South African Journal of Chemical Engineering     Open Access   (Followers: 2)
South African Journal of Chemistry     Open Access   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 5)
Sustainable Chemical Processes     Open Access   (Followers: 2)
Synthesis Lectures on Chemical Engineering and Biochemical Engineering     Full-text available via subscription  
The Canadian Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
The Chemical Record     Hybrid Journal   (Followers: 1)
Theoretical Foundations of Chemical Engineering     Hybrid Journal   (Followers: 2)
Transition Metal Chemistry     Hybrid Journal   (Followers: 2)
Transylvanian Review of Systematical and Ecological Research     Open Access  
Visegrad Journal on Bioeconomy and Sustainable Development     Open Access   (Followers: 1)
Zeitschrift für Naturforschung B : A Journal of Chemical Sciences     Open Access   (Followers: 1)

           

Journal Cover Chemical Engineering Science
  [SJR: 1.073]   [H-I: 135]   [20 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [3039 journals]
  • Residence time calculations for complex swirling flow in a combustion
           chamber using large-eddy simulations
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): A.S. Doost, F. Ries, L.G. Becker, S. Bürkle, S. Wagner, V. Ebert, A. Dreizler, F. di Mare, A. Sadiki, J. Janicka
      In order to appraise the residence time calculation for a fluid element within a complex combustion system, which features oxy-fuel combustion, large-eddy simulations (LES) are carried out under cold flow conditions in a complex swirled flow generic laboratory-scaled combustor. The quantities, like residence time distribution, mean residence time, cumulative distribution function, variance and skewness, are used to characterize the configuration under investigation. To accurately account for the influence of the flow and to capture the tracer concentration evolution, LES are first assessed by comparison with statistical moments from experiments and by various indices of quality and error analysis. They show that the investigated configuration features a non-ideal reactor based on the flow and tracer transport. The calculated residence time distribution is analyzed and compared with experimental findings providing an estimated mean residence time of about τ=1.9s. The derived residence time and functions are afterwards used to make predictions of tracer concentration at the reactor outlet. It turns out that such an appraised LES methodology is able to capture the residence time distribution in an accurate manner which allows its further extension to reacting conditions.


      PubDate: 2016-09-23T17:46:39Z
       
  • Molecular simulation of displacement of shale gas by carbon dioxide at
           different geological depths
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): Haibo Zhang, Dapeng Cao
      The rising worldwide energy demand has greatly stimulated the exploitation of shale gas. Meantime, global warming mainly caused by CO2 emission is a significant concern. As a new scenario, injecting CO2 to displace shale gas is proposed to improve the exploitation efficiency of shale gas and reduce the amount of CO2 emission. In this work, we use a grand canonical Monte Carlo simulation to investigate the displacement of shale gas by CO2 and the sequestration of CO2 simultaneously in a modeled shale matrix at different geological depths from 1 to 4km, where the shale is modeled by inorganic clay mineral and organic matter. We find that both the displacement amount of CH4 and the sequestration amount of CO2 increase with the pore size of the shale at a fixed CO2 injection pressure, which suggests that the hydro-fracturing technology would be very beneficial for displacement exploitation of shale gas. Moreover, we also find that the optimum operating condition for CO2 displacing shale gas is at the depth of 1km, which provides a guidance and reference for displacement exploitation of shale gas by CO2.
      Graphical abstract image

      PubDate: 2016-09-23T17:46:39Z
       
  • A single particle model of lime sulphation with a fractal formulation of
           product layer diffusion
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): Fabio Montagnaro, Marco Balsamo, Piero Salatino
      A fractal-like formulation of the random pore model (RPM) is proposed for the reaction of a gas with a solid, with the rate controlled by both diffusion in the layer of solid product and the kinetics of reaction. This approach gives a time-dependent diffusivity in the product. The model’s predictions are compared with measurements of the removal of SO2 with limestone, carried out in a lab-scale fluidized bed reactor. The fractal-like RPM described the production of CaSO4 better than the standard RPM, which overestimated the uptake of SO2 in the first 40min. The decrease of diffusivity in the product layer with time was ascribed to the degree of crystallization of the product, CaSO4, increasing with time and resulting in a lower ionic mobility in its lattice. The equation proposed is a simple and general one for a gas reacting with a solid (alternative example: the carbonation of lime), whose microstructural properties change significantly with the extent of reaction.


      PubDate: 2016-09-23T17:46:39Z
       
  • Degradation of chloroform by Fenton-like treatment induced by
           electromagnetic fields: A case of study
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): J. Rodríguez-Chueca, A. Mediano, N. Pueyo, I. García-Suescun, R. Mosteo, M.P. Ormad
      The objective of this study of chloroform degradation by the first time through Fenton-like processes induced by electromagnetic fields. Fenton-like processes were carried out at natural pH with 25mg/L of H2O2 and different iron sources: i) FeCl3·6H2O (5, 50 and 100mg/L Fe3+); ii) magnetite (1g/L); iii) clay (80g/L). These treatments were driven in absence and presence of radiofrequency (RF) with an intensity of electromagnetic field of 3.68kA/m. Aqueous solution of chloroform (CHCl3) was also used to study which oxidant species are responsible for the degradation of organic matter. Because of chloroform is scavenger of primary superoxide radicals (•O2 −.) and required of hydroxyl radical for their total degradation. Initial assays of ferromagnetic material/H2O2/RF processes achieved promising results in terms of DOC removal. The highest DOC removal yield (69%) in the treatment of an aqueous solution of CHCl3 was obtained by Fenton/RF treatment using 100mg/L of Fe(III) and 25mg/L of H2O2. In addition, the combination of Magnetite and Fe(III) reached notable values of CHCl3 degradation. The synergetic effect caused by the ferromagnetic properties of Magnetite and the coagulation-flocculation effect caused by iron salts at natural pH is able to reduce the organic matter in water samples. Furthermore, this treatment can be intensified by induction of RF reaching 63% of DOC removal in the CHCl3 solution.
      Graphical abstract image

      PubDate: 2016-09-23T17:46:39Z
       
  • Energy efficiency limits in Photo-CREC-Air photocatalytic reactors
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): Cristina S. Lugo-Vega, Benito Serrano-Rosales, Hugo de Lasa
      Efficiencies in photocatalytic reactors for air treatment have to be established on the basis of Quantum Yields (QY) and Photochemical Thermodynamic Efficiency Factors (PTEFs) using rigorous methods. This involves the evaluation of absorbed photons on the TiO2 using macroscopic balances. These balances have to account for the incident, the reflected and the transmitted radiation. Moreover, hydroxyl radical formation enthalpy is required for PTEF calculations. This proposed methodology is illustrated in the present study using a spray immobilized photocatalyst in a Photo-CREC-Air unit. The operation of this unit with acetaldehyde model compounds provides high and promising maximum QYs of 124%. These experimentally measured QYs are close to the 133% QY anti cipated theoretical limit. Regarding maximum PTEFs, they were 24%, for acetaldehyde, showing a high degree of photonic energy utilization. Results obtained also allow one to establish the energy required for reacting hydroxyl radical formation, key species for converting organic molecules in photocatalysis. These energy demands affect photoconversion rates and efficiency factors, as observed for acetone and acetaldehyde. Results obtained also demonstrate the special value of experimentally established macroscopic balances. Macroscopic balances allow decoupling photocatalyst efficiency and photoreactor efficiency. This approach is critical to clarify key engineering issues for scaling up photocatalytic reactors.
      Graphical abstract image

      PubDate: 2016-09-23T17:46:39Z
       
  • Improvement of oxygen flux through perovskite membranes using a coating of
           ultra-divided particles
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): L. Guironnet, P.-M. Geffroy, N. Richet, T. Chartier
      In the last decades, numerous mixed ionic and electronic conducting materials with a perovskite structure have been investigated for their potential applications as membrane materials for oxygen separation applications. This work shows that significant improvement of electrochemical properties of two perovskite materials, La0.6Sr0.4Fe0.8Co0.2O3-δ (LSFCo6482) and La0.5Sr0.5Fe0.7Ga0.3O3-δ (LSFG5573) is obtained using ultra-divided particles perovskite coating. This coating is obtained by dip-coating thanks to a derived sol-gel synthesis route. The ultra-divided particles have a grain size distribution from 300 to 500nm. The oxygen flux measured using a specific setup shows that the oxygen surface exchange kinetics and bulk diffusion coefficient depend on the microstructure and the chemical composition of the coating material. The relation established between chemical formulation, microstructure, and oxygen flux were used to design optimized membranes.


      PubDate: 2016-09-23T17:46:39Z
       
  • DEM simulation on the packing of fine ellipsoids
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): J.Q. Gan, A.B. Yu, Z.Y. Zhou
      In this work, discrete element method (DEM) is used to study the effect of particle size and aspect ratio on packing structure of fine ellipsoids. It shows that porosity and coordination number significantly change with particle size and shape. The porosity-aspect ratio curve has minima at around 0.5 for oblate spheroids and 1.5 for prolate spheroids, but the cusp at 1.0 varies from convex to concave when particle size reduces as a result of the increasing role of the cohesive forces between particles. The coordination number-aspect ratio curves change from a strong to weak “M” shape when particle size reduces. Based on the results, equations are formulated to describe the correlation between bed porosity, aspect ratio, and particle size or force ratio. Microscopically, the radial distribution function is also affected by both particle size and shape. Fine particles have more disordered structure than coarse particles, and the packing of fine spheres is more ordered than fine ellipsoids. For coarse ellipsoids, majority of particles tend to orient horizontally, but the preferred orientation become worse when reducing particle size.


      PubDate: 2016-09-23T17:46:39Z
       
  • Experimental methodology for study of granular material flow using digital
           speckle photography
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Simon Larsson, Gustaf Gustafsson, Aliae Oudich, Pär Jonsén, Hans-Åke Häggblad
      Granular material flow occurs in many industrial applications, and the characteristics of such flow is challenging to measure. Therefore, an experimental method that captures the flow behavior at different loading situations is desired. In this work, experimental measurements of granular material flow with digital speckle photography (DSP) are carried out. The granular flow process is recorded with a high-speed camera; the image series are then analyzed using the DSP method. This approach enables field data such as displacement, velocity, and strain fields to be visualized during the granular material flow process. Three different scenarios were studied: free surface flow in a fill shoe, flow without a free surface in a fill shoe, and the rearrangement of material in a cavity. The results showed that it is possible to obtain field data of the motion of particles for all three scenarios with the DSP technique. The presented experimental methodology can be used to capture complex flow behavior of granular material.
      Graphical abstract image Highlights fx1

      PubDate: 2016-09-18T13:44:25Z
       
  • Numerical and experimental investigation of hydrodynamics and light
           transfer in open raceway ponds at various algal cell concentrations and
           medium depths
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): Hossein Amini, Abolhasan Hashemisohi, Lijun Wang, Abolghasem Shahbazi, Marwan Bikdash, Dukka KC, Wenqiao Yuan
      A spectral radiation-transport model was integrated with a three dimensional computational fluid dynamics model to simulate the hydrodynamics and light transfer in open raceway ponds (ORPs). The predicted three-dimensional velocity and light intensity agreed well with measured values collected on a lab-scale ORP. However, there was a slight difference in the predicted velocity profiles using two different types of boundaries for the paddlewheel, i.e., the moving zone boundary and inlet velocity boundary, with R 2 values between the predicted and measured velocities of 0.9947 and 0.9838, respectively. The R 2 value between the predicted and measured light intensity was 0.9939. Simulations were further conducted on a large-scale ORP with 100m2 surface area operated at total medium depths of 0.2 and 0.3m, average cell concentration of 0.4g/L, and inlet velocities of 0.1, 0.2 and 0.3m/s from the paddlewheel. The increase of inlet flow velocity from 0.1 to 0.2m/s resulted in a more uniform cell concentration profile. However, when the inlet velocity was further increased from 0.2 to 0.3m/s, there was only a slight increase in the uniformity of the cell concentration. In addition, the simulation results showed that sedimentation of cells more likely occurred at the bottom of the ORP with a total medium depth of 0.2m than at 0.3m at the same inlet velocity. The increase of inlet velocity from the paddlewheel resulted in a uniformly distributed light intensity in the region near the medium surface (e.g., 0.05m depth from the surface) owing to improved mixing. However, owing to a sudden drop in the light intensity after a few centimeters from the medium surface, the cell sedimentation that occurred at the bottom of the ORPs had negligible effects on the light penetration depth in the medium.


      PubDate: 2016-09-18T13:44:25Z
       
  • Propylene epoxidation with hydrogen peroxide in acidic conditions
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): E. Kertalli, L.S. van. Rijnsoever, V. Paunovic, M.F. Neira d'Angelo, J.C. Schouten, T.A. Nijhuis
      In the present work, the epoxidation of propylene with hydrogen peroxide in the presence of acids and halides is studied. The presence of acids and halides is indispensable for increasing the selectivity of the direct synthesis of hydrogen peroxide, the first step of the direct propylene oxide production from hydrogen, oxygen and propylene. Therefore, we focus on the systematic study of the effect of these compounds on the epoxidation of propylene with hydrogen peroxide in prospective of its future integration with hydrogen peroxide in-situ formed. Indeed, the epoxidation of propylene with hydrogen peroxide is the second step of the direct PO synthesis from hydrogen, oxygen and propylene. The acid concentration and type were shown to have an effect on the PO selectivity. Sulphuric and hydrochloric acids, typical compounds used to stabilize the hydrogen peroxide, are not suitable for the direct propylene oxide due to their fast dissociation in the solution. This leads to a fast ring opening reaction of the epoxide. Phosphoric acid was shown to have a much milder effect on the propylene oxide selectivity, therefore being an option for the direct propylene oxide synthesis. Also, the amount of halides (NaBr) needed to stabilize the hydrogen peroxide, does not have an effect on the epoxidation step. Therefore phosphoric acid and NaBr can be implemented in the direct propylene oxide synthesis from hydrogen, oxygen and propylene.


      PubDate: 2016-09-18T13:44:25Z
       
  • Generalized Boltzmann kinetic theory for EMMS-based two-fluid model
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): Bidan Zhao, Shuyue Li, Junwu Wang
      It has long been recognized that the solid particles in circulating fluidized bed risers are distributed heterogeneously in the form of clusters. In response to this fundamental phenomenon, an EMMS-based two-fluid model has been developed recently from the viewpoint of continuum mechanics, however, its microscopic foundation remains unknown. In this study, the statistical mechanics foundation of EMMS-based two-fluid model was presented using generalized Boltzmann kinetic theory. With respect to the gas phase, a new method was developed by considering the fluctuations at different scales simultaneously, with which we can for the first time derive the correct governing equations of gas phase via kinetic theory, in the sense that both the molecular stress and the Reynolds (or pseudo-Reynolds) stress can be obtained simultaneously, whereas all previous kinetic theory analyses failed to predict the appearance of Reynolds (or pseudo-Reynolds) stress in the momentum conservation equation of gas phase due to the assumption of uniform structure, although it is physically always existent no matter how small the Reynolds number is. In case of particle phase, the generalized Boltzmann equation considering the spatio-temporal variation of the volume, density and velocity of clusters was firstly derived, a set of macroscopic transport equations was then derived in different phase spaces. It was shown that the governing equations of dense phase in the EMMS-based two-fluid model derived from continuum mechanics viewpoint corresponds to the macroscopic transport equations at ( r , t ) space. Therefore, present study launches a solid microscopic foundation of EMMS-based two-fluid model. Finally, CFD simulations have been carried out to validate EMMS-based two-fluid model and to study the effect of gas phase pseudo-turbulence.


      PubDate: 2016-09-18T13:44:25Z
       
  • Optimized polybutylene terephthalate powders for selective laser beam
           melting
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): Jochen Schmidt, Marius Sachs, Stephanie Fanselow, Meng Zhao, Stefan Romeis, Dietmar Drummer, Karl-Ernst Wirth, Wolfgang Peukert
      Additive manufacturing processes like selective laser beam melting of polymers (LBM) are established for production of prototypes and individualized parts. The transfer to serial production currently is hindered by the limited availability of polymer powders with good processability. Within this contribution the effect of powder properties, such as particle size, shape and flowability on the processability in LBM and their influence on device quality is exemplified for polybutylene terephthalate (PBT) materials. A process chain for the production of spherical polymer microparticles has been developed to obtain PBT powder materials. The process chain consists of three steps: first, polymer microparticles are produced by wet grinding. Second, the particle shape is engineered by rounding in a heated downer reactor to improve the flowability of the product. Third, a further improvement of flowability of the still cohesive spherical PBT particles is realized by dry coating with fumed silica. Moreover, properties of the PBT powders obtained along the process chain are thoroughly characterized with respect to structure and crystallinity by infrared spectroscopy, X-ray diffraction and differential scanning calorimetry. The effect of flowability, shape and bulk density on the powders’ processabilities in LBM is assessed by characterization of the quality of thin layers built in a LBM device. It is demonstrated that the device quality is strongly determined by particle properties: powders of good flowability and high bulk density are mandatory to obtain dense devices.
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      PubDate: 2016-09-18T13:44:25Z
       
  • Water expandable polystyrene containing cellulose nanofibrils: Expansion
           behavior and morphology
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): Nasser Nikfarjam, Mahmoud Hemmati, Yulin Deng, Nader Taheri Qazvini
      Here, we reported a new type of water expandable polystyrene (WEPS) beads containing cellulose nanofibrils (CNFs). This expansible material, called CNFWEPS, showed the highest expansion ratio (~16) for the as-synthesized beads and ~8 after 4.5 months, which has never been reported in the literature. Expandable beads containing 9–13wt% of the well-dispersed water were synthesized through Pickering emulsion polymerization of styrene in the presence of CNF. During the polymerization, CNFs rearrange and create nanospheres which entrap water inside polystyrene beads. Morphological investigations along with thermogravimetric analysis showed that the entrapped water is either discrete water droplets of 9–10µm in diameter or bound water with a strong adsorption to the hydrophilic nanoparticles inside the beads. Importantly, the bound water could be preserved several months after synthesis and therefore prolong the shelf-life of the CNFWEPS beads. The analysis of the expansion kinetics of the CNFWEPS beads revealed three-regime behavior with strong temperature dependency. The highest expansion ratio was obtained at 135°C for the sample containing 0.2wt% of CNF. Overall, apart from stabilization of water in the beads, the vital role of CNF unveiled to be reinforcing the foam structure and inhibiting the cell wall rupture by increasing melt strength of the matrix during expansion.
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      PubDate: 2016-09-18T13:44:25Z
       
  • Analysis of the state equations of a real gas at high pressures with the
           virial coefficients obtained from controlled chaotic oscillations
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Manuel F. Pérez-Polo, Manuel Pérez-Molina, Elena Fernández Varó, Javier Gil Chica
      This paper investigates several cubic and non-cubic state equations of real gases at high pressures by using the virial coefficients estimated from chaotic oscillations with a mechanical-thermal device. The mechanical part is formed by a cylinder with a piston whose motion is limited by means of a nonlinear spring, a damper and a nonlinear control force to decouple the mechanical and thermal subsystems. To maintain the gas temperature approximately constant, a linear PI controller and a nonlinear control law which manipulates the flow rate of two heating coils inside the cylinder are added. The stability of the mechanical subsystem is analyzed through the first Lyapunov value, whose harmonic variation leads to chaotic behavior with great pressures and an almost constant temperature. The chaotic simulations for nonpolar gases are treated like experimental data to obtain an arbitrary number of virial coefficients which reproduce the state equation in a prescribed pressure range. The validity of the proposed device has been corroborated by using another alternative route to chaos and calculating the fugacity coefficient. The analytical calculations are in good agreement with the numerical simulations.


      PubDate: 2016-09-18T13:44:25Z
       
  • Carbon dioxide rich microbubble acceleration of biogas production in
           anaerobic digestion
    • Abstract: Publication date: 15 December 2016
      Source:Chemical Engineering Science, Volume 156
      Author(s): Mahmood K.H. Al-mashhadani, Stephen J. Wilkinson, William B. Zimmerman
      This paper addresses the use of anaerobic bacteria to convert carbon dioxide to biomethane as part of the biodegradation process of organic waste. The current study utilises gaslift bioreactors with microbubbles generated by fluidic oscillation to strip the methane produced in the gaslift bioreactor. Removal of methane makes its formation thermodynamically more favourable. In addition, intermittent sparging of microbubbles can prevent thermal stratification, maintain uniformity of the pH and increase the intimate contact between the feed and microbial culture with lower energy requirements than traditional mixing. A gaslift bioreactor with microbubble sparging has been implemented experimentally, using a range of carrier gas, culminating in pure carbon dioxide, in the anaerobic digestion process. The results obtained from the experiments show that the methane production rate is approximately doubled with pure carbon dioxide as the carrier gas for intermittent microbubble sparging.
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      PubDate: 2016-09-18T13:44:25Z
       
  • Modeling simultaneous deposition and aggregation of colloids
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Stefano Lazzari
      Solid formation and particle deposition in chemical and pharmaceutical processes often leads to heat exchanger or reactor fouling, compromising operability. The aim of this work is to propose a mathematical framework, based on population balance equations, to describe the simultaneous colloid aggregation and deposition. The problem is dealt with by accounting for two distinct cluster mass distributions, the first one describing the free clusters, while the second one the deposited aggregates. Three main events are considered: (i) aggregation of two free clusters, (ii) deposition of free clusters on the reactor wall (i.e. a free cluster turns into a deposited one), and (iii) aggregation of a free cluster with a deposited one. To describe the aggregation of free clusters, three typical aggregation kernels (i.e. diffusion-limited and reaction-limited cluster aggregation as well as simple shear aggregation) have been used. Starting from those kernels, aggregation laws to describe the interaction between a free and a deposited cluster were proposed and a simple cluster-mass dependent deposition law was employed. The simulation results are then discussed in the frame of one dimensionless parameter, function of the relevant characteristic time of the process (i.e. aggregation and deposition).
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      PubDate: 2016-09-11T14:26:39Z
       
  • Experimental investigation on pressure drop and heat transfer in metal
           foam filled tubes under convective boundary condition
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Hui Wang, Liejin Guo
      Heat transfer under convective boundary condition is common in heat exchangers. This paper presented the experimental results of air flow and heat transfer through three stainless steel foam filled tubes under convection boundary condition. The air flow velocity inside the tube is relatively high, which varied from 7.0 to 26.0m/s. The stainless steel foam filled tubes, manufactured using high-temperature metallic sintering technique, are of different pore densities (10, 30 and 70 PPI) but have the same porosity of 0.93. The air pressure drop through the stainless steel foam filled tubes was measured. It was found that the inertial drag is the dominant part of the pressure drop at higher velocity. The pressure drop experimental data under high velocity were compared to the predictions by the correlations obtained under relatively low velocity and great discrepancies have been found. A new correlation for the pressure drop through metal foams under high velocity was presented. The effect of the boundary condition on the heat transfer performance was addressed by the comparison of Nusselt number obtained in the present study with that obtained under constant heat flux boundary condition in the published investigation. It was found that the Nusselt number obtained under convective boundary condition is much lower than that obtained under constant heat flux boundary condition. A new correlation for Nusselt number under convective boundary condition was developed.


      PubDate: 2016-09-06T16:35:25Z
       
  • Droplet in droplet: LBM simulation of modulated liquid mixing
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Yuhang Fu, Lin Bai, Shufang Zhao, Kexin Bi, Yong Jin, Yi Cheng
      Mixing inside a double-emulsion droplet was investigated by using a ternary lattice Boltzmann method coupled with a passive tracer model. The specific attention was paid to the mixing modulation by controlling the movement of the inner droplet, where several moving modes following straight, circular or Lissajous trajectories were assigned arbitrarily. The simulations showed that the mixing performance can be intensified to different extent since the motion of inner droplet causes a recirculation inside the double emulsion. We further demonstrated that the initial distribution of species to be mixed played another significant role in the mixing performance. It is therefore suggested that cooperation between the initial distribution of passive tracer and moving mode of the inner droplet should be taken into consideration to better modulate the mixing inside droplet when designing the geometries for droplet-based microfluidics.


      PubDate: 2016-09-06T16:35:25Z
       
  • Incorporation of 10-hydroxycamptothecin nanocrystals into zein
           microspheres
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Guijin Liu, Shaomin Li, Yinxia Huang, Hongdi Wang, Yanbin Jiang
      Incorporation of drug nanocrystal (DNC) into a particulate carrier to form the DNC delivery system was conducted in this study, where 10-hydroxycamptothecin (HCPT) was selected as the model drug and zein was the carrier. The supercritical anti-solvent (SAS) process or the built-in ultrasonic dialysis process (BUDP) was applied to prepare HCPT NC-loaded zein microspheres (HCPT NC-Zein MS) at first respectively, but the results showed that the products obtained were unsatisfactory in their particle microstructures. Fortunately, by combining the SAS process with BUDP, i.e. the co-precipitation of HCPT and zein prepared using the SAS process was dispersed into ethanol–water as the dialysis solution for BUDP, the results showed that desirable HCPT NC-Zein MS were obtained. The formulations were evaluated quantitatively by an overall desirability function (DF), and the optimized HCPT NC- Zein MS was prepared according to the range analysis results of DF. Under the optimized conditions, HCPT NC-Zein MS with a mean particle size=1.10±0.12µm, drug loading=5.98% and encapsulation efficiency=95.68% were obtained. The further characterizations of SEM, FT-IR, XRD and DSC demonstrated that HCPT NC was successfully incorporated into the interior of zein microspheres. The effects of the process parameters and the formation mechanism of HCPT NC-Zein MS were discussed in detail. Furthermore, it is presented that HCPT NC-Zein MS sustained HCPT release rate successfully, where about 50% HCPT was fast released in the first 20h, then the release trend followed zero order kinetics and reached 70% in 82h.
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      PubDate: 2016-08-27T23:38:56Z
       
  • Capacity and absorption rate of tertiary and hindered amines blended with
           piperazine for CO2 capture
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Yang Du, Ye Yuan, Gary T. Rochelle
      Aqueous piperazine (PZ) blended with a tertiary or hindered amine combines the high CO2 capacity of the tertiary or hindered amine with the fast rate of PZ. For flue gas CO2 capture, the optimum pKa (that which offers the highest CO2 cyclic capacity) of a mono-tertiary amine blended with PZ is 9.1. A generic Aspen Plus® model for PZ/tertiary amine was developed to predict the CO2 vapor-liquid-equilibrium (VLE) from the pKa of the tertiary amine. The polarity of the tertiary amine also affects the CO2 solubility of the PZ/tertiary amine. Hindered amines that form little carbamate show similar CO2 VLE to tertiary amines with the same pKa, when blended with PZ. The CO2 absorption rate of most 2.5m PZ/2.5m tertiary amines was slightly slower than 2.5m PZ, probably due to the higher viscosity of the blends.


      PubDate: 2016-08-27T23:38:56Z
       
  • Micromixing efficiency of a novel helical tube reactor: CFD prediction and
           experimental characterization
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Jiang-Zhou Luo, Yong Luo, Guang-Wen Chu, Moses Arowo, Yang Xiang, Bao-Chang Sun, Jian-Feng Chen
      A novel helical tube reactor (HTR) consisting of a pre-mixer and a helical tube was designed for mixing and reaction process intensification. The pre-mixer was used to adjust and change the premixing behavior between the involved reactants, which eventually determines the environment for micromixing. Two types of pre-mixers, co-current flow pre-mixer (CCM) and cross-flow pre-mixer (CRM), were employed and their mixing performance was studied by computational fluid dynamics (CFD) simulations. Results revealed that the CRM has better mixing performance than the CCM, suggesting that the predicted micromixing efficiency of the HTR consisting of the CRM (CRM-HTR) may be better than that comprising the CCM (CCM-HTR). Furthermore, the iodide–iodate reaction system was used separately to characterize the micromixing efficiency of the HTR comprising the different types of pre-mixers, and the results are in agreement with those of CFD which predicted better micromixing performance in the CRM-HTR than the CCM-HTR. Additionally, the effects of feed position and initial dispersion size of acid solution, volumetric flow ratio, and viscosity on micromixing efficiency of the CRM-HTR were investigated. A comparison between the CRM-HTR and a straight tube reactor (CRM-TR) with a length equivalent to that of the CRM-HTR revealed that CRM-HTR has better micromixing efficiency. Moreover, the effects of curvature ratio and number of turns on micromixing efficiency of the CRM-HTR were also conducted. The results demonstrated that the curvature ratio had an important influence on the micromixing. This work shows that the novel CRM-HTR has great potential for chemical reaction process intensification.


      PubDate: 2016-08-27T23:38:56Z
       
  • Computer virtual experiment on fluidized beds using a coarse-grained
           discrete particle method—EMMS-DPM
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Liqiang Lu, Ji Xu, Wei Ge, Guoxian Gao, Yong Jiang, Mingcan Zhao, Xinhua Liu, Jinghai Li
      Virtual process engineering (VPE) aims to redefine the roadmap for process scaling-up and optimization, from stepwise experiments to high-performance computer simulations. This is a long-cherished dream of chemical engineers, but requires high standards of Accuracy (the agreement between the simulation and the real process), Capability (the computational speed, scale, and resolution of the simulation), and Efficiency (cost-effective and easy to use), in short, ACE. For complex processes such as gas–solid fluidization, the gap between state-of-the-art simulations and VPE is still huge in terms of ACE. However, the work reported in this paper narrows this gap significantly. In this study, a coarse-grained discrete particle method (DPM) defined by the energy-minimization multi-scale (EMMS) model is deployed for high-resolution simulations of fluidized beds, with the gas- and solid-phase equations solved concurrently by CPUs and GPUs in a heterogeneous supercomputing system. With systematic optimization of the model, numerical method, software, and hardware, we are able to simulate lab- to pilot-scale fluidized beds at quasi-realtime speed, and conduct virtual experiments on such systems. This enables very-long-time simulations to obtain important engineering parameters such as the particle residence time distribution, attrition and deactivation indexes. This work demonstrates that the industrial application of VPE is almost on the horizon.
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      PubDate: 2016-08-24T13:10:30Z
       
  • Engineered polymeric nanoparticles of Efavirenz: Dissolution enhancement
           through particle size reduction
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): B.N. Vedha Hari, Cui-Lin Lu, N. Narayanan, Rui-Rui Wang, Yong-Tang Zheng
      Solubility and bioavailability of drug molecules are the key factors influencing their therapeutic effectiveness in-vivo. The desired drug concentration in systemic circulation can be achieved through the required dissolution of the drug in the biological environment which ultimately affects the pharmacological response. Efavirenz is an anti-HIV molecule with low solubility and variable bioavailability (<45%) and prescribed as first line drug with 800mg dose. The objective of the study was to develop polymeric nanoparticles of Efavirenz and assess the dissolution enhancement, safety and efficacy using T-lymphatic cell lines infected with HIV-1IIIB strain. The nanoparticle formulations were developed using solvent evaporation method and characterized for its size (110–283nm), charge (−21 to −33mV), % entrapment efficiency (57–95%), viscosity of nanosuspension (2.39–4.2cP) and surface area of the particles (1.4m2/g). The fourier transform infrared analysis and differential scanning calorimetry analysis of the pure drug and nanoparticles revealed the compatibility and stability of drug in nanoparticles. The in-vitro dissolution studies of the nanoparticles in distilled water media using type-1 USP dissolution apparatus at 100rpm showed improved drug release based on the polymer composition, as compared with marketed formulations (capsules). The cytotoxicity and therapeutic activity of nanoparticles was studied by MTT assay in C8166 cell lines and syncytium formation assay using HIV-1IIIB strain infected cell lines, respectively. Cell uptake of the nanoparticles was studied by confocal microscopy. The formulated nanoparticles were found to be safe and exhibiting 2-fold increase in therapeutic activity compared to pure drug, which could be attributed to improved dissolution and high cell uptake.
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      PubDate: 2016-08-24T13:10:30Z
       
  • Oxidative destruction of monocyclic and polycyclic aromatic hydrocarbon
           (PAH) contaminants in sulfur recovery units
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Ramees K. Rahman, Salisu Ibrahim, Abhijeet Raj
      The requirement of low sulfur content in fuels and the stringent environmental regulations has led to an increased production of acid gas (H2S and CO2) as byproducts in oil and gas industry. Consequently, the need for economic and efficient treatment of acid gas has surfaced. Sulfur recovery units (SRU), consisting of a furnace and catalytic reactors, are widely deployed to recover sulfur and thermal energy from acid gas. The contaminants in acid gas such as benzene, toluene, ethylbenzene, and xylenes (BTEX) and frequent changes in its composition cause flame instability and produce unwanted byproducts such as polycyclic aromatic hydrocarbons (PAHs), CO, COS, and CS2, which reduce process efficiency and increase operational cost through frequent catalyst deactivation. In this paper, a detailed reaction mechanism is presented for SRU that includes reactions for the combustion of acid gas and its contaminants, and the formation and oxidation of large PAHs by several oxidants (O, O2, OH, and SO2). The mechanism is validated with different sets of experimental data, and is used to investigate the process conditions that triggers the oxidative destruction of aromatics (BTEX and PAHs) in the furnace. With decreasing acid gas flow rate, and increasing feed preheating temperatures and oxygen concentration in air, the aromatics concentration was found to decrease substantially due to their enhanced oxidation by SO2 and O2, which indicates that the destruction of harmful aromatics in the high-temperature zone of the furnace is possible with optimized SRU process conditions. The developed reaction mechanism provide viable means of optimizing SRU to achieve aromatics destruction, enhanced catalyst life, and reduced sulfur production cost.


      PubDate: 2016-08-24T13:10:30Z
       
  • Novel C-PDA adsorbents with high uptake and preferential adsorption of
           ethane over ethylene
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Xingjie Wang, Ying Wu, Xin Zhou, Jing Xiao, Qibin Xia, Haihui Wang, Zhong Li
      In this work, a novel porous carbon-based material C-PDA(Carbonized Polydopamine Adsorbent) was prepared using one-step synthesis method for adsorption separation of C2H6/C2H4, and then characterized by N2 adsorption at 77K, FTIR, XPS and TG. The BET surface area and pore volume of C-PDAs can reach as high as 3291m2/g and 1.97 m3/g, respectively. FTIR spectra suggested the presence of N/O functionalities in C-PDAs, and its contents decreased with the KOH/C ratio at which the samples were prepared. Adsorption capacity of C-PDAs for C2H6/C2H4 increased with the surface N and O contents of C-PDAs. More interestingly, it showed significantly preferential adsorption of C2H6 over C2H4. Its C2H6 adsorption capacity was up to 7.93mmol/g at 100kPa, and its C2H6/C2H4 adsorption selectivity was in the range of 1.9–7.94 at pressure below 100kPa when the ratio of C2H6:C2H4 was 0.1:0.9 at 298K, higher than most reported adsorbents possessing preferential adsorption of C2H6 over C2H4. The preferential adsorption mechanism of C2H6 over C2H4 on C-PDAs were revealed by DFT (Density functional theory) calculation. The isosteric heat of C2H6 and C2H4 adsorption on C-PDAs were much lower than the preferential adsorption affinity of olefin over π-complexation sorbents. These excellent adsorption properties of C-PDAs make it a type of promising adsorbent for the effective separation of ethane/ethylene.
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      PubDate: 2016-08-24T13:10:30Z
       
  • Pressure drop study on packings of differently shaped particles in
           milli-structured channels
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): S. Hofmann, A. Bufe, G. Brenner, T. Turek
      Pressure drop measurements and calculations were carried out for differently shaped packings of particles (315–1000µm) in milli-structured reactors with slit widths of 1.5–3mm. It could be shown that the wall effect in these packings with D/d ratios between 6 and about 14 must be taken into account while laminar flow dominates for the employed Reynolds numbers in the range 0.5<Re ε<12. Although developed for cylindrical packings, earlier proposed pressure drop correlations including wall effect terms can be also applied to slit-type channels. For prediction of pressure drops over packings of non-spherical particles it is recommended to evaluate the results with the volume-equivalent sphere diameter which is corrected by the sphericity instead of the Sauter diameter. An exact prediction of the pressure drop, however, is only possible if the sphericity is used as a fitting parameter. Furthermore µ-tomographic scans of real packings were used to describe the geometry for pore scale resolving simulations of the flow and pressure drop calculations using the lattice-Boltzmann method. While an excellent agreement between measurements and simulations was achieved for the non-spherical catalyst particles, the simulations slightly overestimated the pressure drop for the glass beads. These deviations are most probably due to artefacts occurring during the binarization procedure of the scans.
      Graphical abstract image

      PubDate: 2016-08-24T13:10:30Z
       
  • Phase equilibrium and formation behaviour of CO2-TBAB semi-clathrate
           hydrate at low pressures for cold storage air conditioning applications
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Xiaolin Wang, Mike Dennis
      Cold thermal storage has been widely used in air conditioning systems. For electric air conditioning, it helps to shift the peak load on electricity grids; for solar cooling, it enables cooling supply during solar outages. CO2 hydrate has been proposed as a cold storage medium for its suitable phase change temperature and large latent heat. Tetra-n-butyl ammonium bromide (TBAB) has been studied to moderate the formation pressure of CO2 hydrate. In this study, formation and dissociation of CO2-TBAB semi-clathrate hydrate were conducted at low pressures (<10bar) applicable to the operating conditions of air conditioning systems. The hydrates were formed with the TBAB mass fraction of 10, 20 and 32wt%. Using the T-history method, the formation enthalpy of CO2-TBAB semi-clathrate hydrate was measured in a self-fabricated reaction tube. In addition, the formation behaviour of CO2-TBAB semi-clathrate hydrate, namely the CO2 gas uptake, the induction time and the supercooling degree, were investigated under various feed pressures and heat transfer fluid (HTF) temperatures. Besides, secondary promoters (tetra-n-butylammonium fluoride (TBAF) at the mass fraction of 0.1, 0.5, 2.0 and 3.5wt%, sodium dodecyl sulphate (SDS) at the mass fraction of 0.1, 0.3 and 0.5wt%, and TiO2 nanoparticle in 20 and 80nm) were used to aid the hydrate formation. The aim of this study is to reduce the capital and operating cost of a CO2 hydrate cold storage system by increasing the gas uptake, decreasing the supercooling degree and shortening the induction time.


      PubDate: 2016-08-24T13:10:30Z
       
  • Compromise between minimization and maximization of entropy production in
           reversible Gray–Scott model
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Wen Lai Huang, Jinghai Li
      In this work, the evolution of entropy production in the Gray–Scott model (P. Gray and S. K. Scott, Chemical Engineering Science 38 (1983) 29–43) is investigated for four representative cases within three regimes. It is revealed that the extremal trends of entropy production for these cases are regime-dependent. In the monostable regime without heterogeneous structures, the steady state follows the minimization of entropy production. For the bistable uniform regime, the steady state with higher entropy production prevails over that with lower entropy production. As to the heterogeneous states that emerge around the bifurcation curves, the entropy production varies in both space and time, showing alternate appearance of states corresponding to minimum and maximum values of entropy production, respectively. The spatiotemporal compromise between maximization and minimization of entropy production appears to govern the corresponding steady states in different regimes.
      Graphical abstract image

      PubDate: 2016-08-19T13:06:16Z
       
  • Nucleation behavior of eszopiclone-butyl acetate solutions from metastable
           zone widths
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Shijie Xu, Jingkang Wang, Keke Zhang, Songgu Wu, Shiyuan Liu, Kangli Li, Bo Yu, Junbo Gong
      Experimental data on the critical supercooling ∆T max, a measure of metastable zone width (MSZWs), as a function of saturated temperature T 0 and cooling rate R were analyzed to describe the nucleation behavior of unseeded eszopiclone-butylacetate solutions. The Nývlt's semiempirical model and Sangwal's theory were employed, respectively. And moreover, we propose a modified model based on the Sangwal's theory in which the nucleation parameters are not dependent on saturation temperature T 0 and nucleation temperature T 1 which can fit the experimental data better than Sangwal's theory. Furthermore, the pre-exponential A and solid–liquid interfacial energy γ can be obtained by employing this modified model, thus, sheds light on the relationship between nucleation parameters and the cooling rate R. Meanwhile, based on the Classical Nucleation Theory, with the estimated interfacial energies from the slope in the modified model, the critical nucleus size and critical Gibbs free energy were calculated and discussed. Then based on the Sangwal's theory, the nucleation activation barrier is found to be dependent on ln R with an exponential relationship, hence, the relationship between nucleation barrier and pre-exponential A can be constructed. At last, the effects of agitation rate and working volume on MSZWs were investigated and discussed.


      PubDate: 2016-08-19T13:06:16Z
       
  • Modeling the change in particle size distribution in a gas-solid fluidized
           bed due to particle attrition using a hybrid artificial neural
           network-genetic algorithm approach
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Amir Abbas Kazemzadeh Farizhandi, Han Zhao, Raymond Lau
      Particle size distribution (PSD) is an important parameter in gas-solid fluidized bed. The change in PSD due to particle attrition can affect the long-term performance of fluidized bed. In this study, artificial neural network (ANN) with genetic algorithm (GA) as a meta-modeling tool was employed to model the change in PSD during fluidization. Experiments were conducted using incineration bottom ash (IBA) as the fluidizing particles and different mass percentage of large and small glass beads were used as the grinding medium. Rosin–Rammler (RR) distribution was used to describe the IBA PSD. The ANN-GA models developed were subsequently used to study the effect of fluidization time, mass percentage of glass beads and size of glass beads used on the IBA particle attrition during fluidization.
      Graphical abstract image

      PubDate: 2016-08-19T13:06:16Z
       
  • Fluid and particle coarsening of drag force for discrete-parcel approach
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Ali Ozel, Jari Kolehmainen, Stefan Radl, Sankaran Sundaresan
      Fine-grid Euler–Lagrange simulations of gas-fluidization of uniformly sized particles have been performed in three-dimensional periodic domains. Snapshots obtained from these simulations have been systematically coarse-grained to extract filter size dependent corrections to the drag law that should be employed in coarse Euler–Euler (EE) simulations. Correction to the drag law that should be employed in Coarse Multi-Phase Particle-in-Cell (MP-PIC) model simulations is examined through a two-step process: separating the coarsening of the fluid and particle phases. It is found that the drag correction is almost entirely due to the coarsening of the fluid cells, with particle coarsening having only a weak effect. It is shown that drag correction for coarse EE and MP-PIC simulations are comparable. As a result, coarse drag models developed for EE simulations can serve as a good estimate for corrections in MP-PIC simulations, and vice versa.
      Graphical abstract image Highlights fx1

      PubDate: 2016-08-19T13:06:16Z
       
  • Practical designs of membrane contactors and their performances in CO2/CH4
           separation
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Seong-Joong Kim, Ahrumi Park, Seung-Eun Nam, You-In Park, Pyung Soo Lee
      Porous polypropylene (PP) hollow fiber membrane contactors operated by either single absorption processes or combined absorption/desorption processes using water have been investigated for use in the production of biomethane from simulated biogas. To observe the effect of operating parameters on the membrane contactors, the connection of modules, flow rates, and operating pressures were tuned. For CO2/CH4 separation, operations using single absorption processes produced a good yield (85%) of high purity CH4 (97%). Connections in series containing two absorption modules facilitated CO2 absorption due to an increase in contact area at the liquid–gas interface. In the combined absorption/desorption processes, CH4 was recovered in 75% yield and 98% purity using two 1″ absorption modules and four 2″ desorption modules connected in series. Although the results were somewhat poorer than those of the single absorption processes due to limits in desorption performance, the combined process provided the potential for producing renewable methane as a fuel for vehicles. Furthermore, for the single absorption processes, the PP hollow fiber membrane contactor was operated continuously, while the membrane used in the combined absorption/desorption processes required periodic maintenance to maintain an acceptable performance.


      PubDate: 2016-08-19T13:06:16Z
       
  • Pyrolysis and catalytic upgrading of low-rank coal using a
           NiO/MgO–Al2O3 catalyst
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Yi Li, Muhammad Nadeem Amin, Xingmei Lu, Chunshan Li, Fuqiang Ren, Suojiang Zhang
      The catalyst NiO/MgO–Al2O3 was prepared by loading magnesium and nickel onto the surface of γ-Al2O3 beads, respectively, and was adapted to in situ upgrade the high temperature pyrolysis vapor derived from coal pyrolysis. The catalyst synthesis process, and structural variation were characterized by the XRD, SEM, and physical adsorption analyzer. In order to examine the catalytic effect on the different nickel loading ratio in the catalysts, the solid–liquid–gas product distribution, variation of gas and components of coal tar were studied by simulated distillation, GC/MS, elemental analysis and so on. The results shows both the tar yield and the content of the light fraction in the tar can be increased by catalytic up grade. The catalyst has a strong ability to convert the heavy component and polycyclic aromatic hydrocarbons in the tar to lower molecular weight components.


      PubDate: 2016-08-19T13:06:16Z
       
  • Kinetic investigations of the steam reforming of methanol over a
           Pt/In2O3/Al2O3 catalyst in microchannels
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): M. Wichert, R. Zapf, A. Ziogas, G. Kolb, E. Klemm
      A kinetic study of methanol steam reforming over bimetallic Pt/In2O3/Al2O3 catalyst was carried out. The kinetic measurements were performed in a microstructured monolithic reactor with an external recycle free of temperature and concentration gradients. By the help of residence time distribution measurements it could be verified that the reactor showed the behaviour of an ideal continuous stirred tank reactor (CSTR). The absence of external and internal concentration gradients could be proven by corresponding experiments and theoretical diagnostic criteria. The kinetic measurements performed by variation of the reactant inlet partial pressures revealed that in the temperature range from 310°C to 355°C the molar rate of methanol consumption mainly depends on the methanol partial pressure, especially at higher temperatures, whereas there is only minor dependence on the water partial pressure. Carbon dioxide has no inhibiting effect, whereas hydrogen showed a weak inhibiting effect. Two power laws and three Langmuir-Hinshelwood rate equations were created for the modelling of the kinetic data. Power laws could not be fitted to the measured values. Therefore the uses of Langmuir-Hinshelwood rate laws with temperature dependent sorption constants are inevitable for the modelling. The model discrimination revealed that the rate law derived from a mechanism, which assumes the dehydrogenation of an adsorbed methoxy-species as rate determining step, described the measured kinetic data second best. Optimum agreement between observed and predicted molar rates of methanol consumption was obtained when applying a Langmuir-Hinshelwood rate law assuming dissociative methanol and molecular water adsorption on the catalyst surface. Dissociative adsorption of water and methanol at the same active site may be excluded. This leads to a better evaluation of the models that assume molecular water adsorption at the same site where methanol ties or the ones with no participation of water in the rate determining step (RDS) under discrimination.


      PubDate: 2016-08-19T13:06:16Z
       
  • Mean penetration depth of metals in hydrodemetallation catalysts
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Loïc Sorbier, Frédéric Bazer-Bachi, Maxime Moreaud, Virginie Moizan-Basle
      A descriptor has been proposed, the mean penetration depth, to characterize the deposit profiles of metals in hydrodemetallation catalysts. This mean penetration depth can be obtained from concentration maps or profiles of elements along catalyst cross sections using local characterization techniques. This descriptor is well suited even for very irregular shapes such as multilobed extrudates often encountered in industrial catalysts. Using a very simple model of metal deposit, the mean penetration depth can be analytically related to the Thiele modulus of the deposit reaction and consequently to the catalyst efficiency for trivial shapes (infinite slab, infinite cylinder and sphere). The mean distance to the surface of the catalyst pellet is found to be the convenient quantity to renormalize Thiele modulus and mean penetration depth to obtain an universal curve independent of the catalyst pellet shape. An example of application is given on a used hydrodemetallation catalyst of tetralobed shape.
      Graphical abstract image Highlights fx1

      PubDate: 2016-08-19T13:06:16Z
       
  • Experimental and computational study of a high speed pin mixer via PEPT,
           visualization and CFD
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Anne K. Konz, Erich Windhab
      Continuous high speed pin mixers have been successfully implemented industrially to mix high fractions of powders into highly viscous non-Newtonian liquids. However, they have not been described in the literature yet. This work presents a multi-method approach, consisting of conventional torque and throughput measurements to calculate average residence times and dimensionless Reynolds/power numbers for suspension mixing, Positron Emission Particle Tracking (PEPT) to gain information on particle trajectories and velocities in the investigated opaque model system, high speed film visualization and CFD simulations. By the combination of these methods, valuable information on the influence of variable process parameters, particularly on the influence of pin configuration, pin shape and inclination of semi-cylindrical pins on mixing mechanisms and efficiency, could be gathered for a broad range of viscosities and powder fractions in Newtonian and non-Newtonian fluids. Flow patterns such as a “Split-and-Recombine” convection pattern at the pins, axial mixing mechanisms and beneficial process conditions to reduce particle sedimentation caused by centrifugal forces in the mixer were retrieved from the results. The PEPT methodology was successfully implemented for a high-shear continuous mixing process of suspensions for the first time. As the combined methodology shows reasonable and reliable results that were also applicable at industrial scale, the work provides sound basis for further research development of measurement techniques for other mixing processes, especially in opaque systems.


      PubDate: 2016-08-19T13:06:16Z
       
  • Ceramic block packing of Honeycomb type for absorption processes and
           direct heat transfer
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Rumen Darakchiev, Simeon Darakchiev, Daniela Dzhonova-Atanasova, Svetoslav Nakov
      Ceramic block packing of Honeycomb type has been developed and studied for the purpose of absorption and heat transfer processes in column apparatuses. The packing design ensures high efficiency at relatively low pressure drop. The packing is easy to manufacture and the ceramic is resistant to high temperatures and chemically aggressive environments. Detailed studies on the characteristics of mass transfer and fluid flow have resulted in development of a reliable methodology for design of packed columns for absorption processes and direct heat transfer. Their successful implementations in the chemical industry, for environmental protection, and in the power production have confirmed the validity of the methodology. The Honeycomb packing is used in an industrial system for purification of process gases from H2S in staple cellulose fiber production, which operates with a degree of absorption greater than 99%. The packing is employed in industrial systems for heat recovery of flue gases from boilers burning natural gas, which utilize up to 13–15% extra heat and significantly reduce the harmful emissions. The heated and humidified air for combustion in one of the variants creates special conditions for fuel combustion such that the formation of nitrogen oxides is decreased by 3.5 times.


      PubDate: 2016-08-15T02:51:47Z
       
  • Heterogeneous reactive extraction for isopropyl alcohol liquid phase
           synthesis: Microkinetics and equilibria
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Vanessa Walter, Bernhard Pfeuffer, Ulrich Hoffmann, Thomas Turek, Detlef Hoell, Ulrich Kunz
      The reaction kinetics for the liquid phase synthesis of isopropyl alcohol (IPA) from propene (P) and water (W) using a macroporous sulfonic acid ion exchange resin as catalyst were determined experimentally in a multiphase CSTR in the temperature range 398K to 433K at 8MPa. This high pressure is necessary to dissolve propene in the aqueous phase and to ensure a liquid or supercritical state of all components. At typical reaction conditions, the reactants form two immiscible phases; the reaction takes place in the water swollen gel phase of the catalysts microspheres. Due to the large excess of water in the gel phase the compositions in the gel phase, in the macropore fluid, and in the catalyst surrounding aqueous phase are assumed to be identical. For temperatures up to 413K the reaction kinetics for the used catalyst size are not influenced by mass transfer resistances within the catalyst matrix. Two reactions, the formation of IPA and the condensation reaction of two IPA molecules forming the by-product diisopropyl ether (DIPE), are investigated. The experimental results can be described sufficiently by pseudo-homogeneous rate expressions in aqueous phase activities. For the formation of IPA, the forward reaction is first-order in propene and water while the reverse reaction is first-order in IPA. The activation energy of the forward reaction was determined to 115.3kJ/mol. The formation of DIPE is second order with respect to the activity of IPA. The reverse reaction is first order with respect to the activities of DIPE and water. The activation energy was determined to 85.6kJ/mol. Simultaneous chemical and phase equilibria were investigated theoretically using the volume translated Peng-Robinson equation of state (VTPR-EoS) in combination with a g E-mixing rule. Parameters of the used g E-model were adjusted to experimental liquid-liquid equilibrium (LLE) data.


      PubDate: 2016-08-15T02:51:47Z
       
  • Adsorption of mixed DDA/NaOL surfactants at the air/water interface by
           molecular dynamics simulations
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Li Wang, Runqing Liu, Yuehua Hu, Wei Sun
      The adsorption behavior of mixed cationic dodecylamine (DDA)/anionic sodium oleate (NaOL) at different molar ratios at the air/water interface were investigated using molecular dynamics (MD) simulations. Some parameters such as the distribution of headgroups, carbon chains, counterions and water, as well as the headgroups-water radial distribution function, were calculated. The simulation results show that compared to pure DDA and NaOL, their mixtures are more compact and can form a tight monolayer at the air/water interface, indicating higher surface activity. The polar groups of surfactants are tilted into the liquid phase because of strong interactions with water; meanwhile, the hydrophobic carbon chains stretch towards the air phase at a smaller angle than pure surfactant. Water molecules can gather easily and aggregate around the headgroups in the mixed surfactants system. The order of the surface activity is as follows: DDA/NaOL=1/3>DDA/NaOL=1/1> DDA/NaOL=3/1. These results demonstrate a strong synergistic interaction between DDA and NaOL at the air/water interface.
      Graphical abstract image

      PubDate: 2016-08-15T02:51:47Z
       
  • Methodology for evaluating modular production concepts
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Stefan Sievers, Tim Seifert, Gerhard Schembecker, Christian Bramsiepe
      A more flexible and efficient production of chemicals is a requirement for further strengthening the competitiveness in the chemical industry. An approach proposed to achieve this is modular plant design. It offers new opportunities for the supply chain and combines production flexibility and efficiency. However, modular facilities are expected to be built at comparably small scales and loss of economy of scale is a major concern. There is a need to know under which conditions a modular plant design is a beneficial option. Addressing this it would be helpful to have a methodology that includes modeling of production scenarios in a holistic way including supply chain and process simulation and thus allowing a meaningful evaluation. For that reason we developed such a methodology, using the F3 factory concept as an example for modular plant design. Demonstrating the methodology's feasibility an exemplary implementation in a software tool was established enabling comparative simulation and evaluation of batch, continuous and the modular F3 factory production. As unique feature supply chain and process simulation is combined in a single software implementation allowing for statistical analysis to automatically evaluate the economic performance of production concepts under different boundary conditions of the process and the supply chain. The incorporation of those boundary conditions is usually not part of process simulation and goes beyond state of the art approaches. In this paper, the methodology implemented will be presented and the application will be demonstrated using two production scenarios as examples. For the examples investigated, it was found that compared to the conventional production concept the modular F3 factory concept is economically robust concerning the choice of design capacity with regard to diverse market conditions.


      PubDate: 2016-08-15T02:51:47Z
       
  • Synthesis of mesoporous materials SBA-16 with different morphologies and
           their application in dibenzothiophene hydrodesulfurization
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Zhengkai Cao, Peng Du, Aijun Duan, Rong Guo, Zhen Zhao, Hong lei Zhang, Peng Zheng, Chunming Xu, Zhentao Chen
      A series of mesostructured SBA-16 materials with different morphologies were prepared by templating method using triblock copolymer pluronic F127 (EO106PO70EO106) as surfactant and tetraethyl orthosilicate (TEOS) as silicon source. The influences of inorganic salt KCl and the synthesis temperature (temperature of the synthesis process before hydrothermal treatment) from 25 to 55°C on the morphologies of SBA-16 materials were also investigated. The obtained materials were characterized by various techniques, including X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), scanning electron microscope (SEM), transmission electron microscopy (TEM), N2 adsorption–desorption, UV–visible diffuse reflectance spectrum (UV–vis DRS), H2 temperature-programmed reduction (H2-TPR), Raman and X-ray photoelectron spectra (XPS) measurements. The SAXS, SEM and TEM results demonstrated that the SBA-16 materials possessed a body-centred cubic Im3m mesostructure. Five kinds of morphologies were found for the as-prepared SBA-16 materials, while sphere SBA-16 particles were obtained at the synthesis temperatures of 25°C and 30°C; mixed states of decahedral together with sphere were obtained at 38°C; decahedral together with dodecahedral was obtained at 45°C; hexagonal prisms was obtained at 50°C; and tetrakaidecahedron was obtained at 55°C. Moreover, aluminium isopropoxide was incorporated into the SBA-16 materials with a Si/Al molar ratio of 20 through the post-synthesized method, and the corresponding hydrodesulfurization (HDS) activities of NiMo supported catalysts on dibenzothiophene (DBT) were also performed in a micro reactor at T=340°C and P=4MPa with different weight hourly space velocities (WHSV). These NiMo catalysts were denoted as NiMo/S-x. S referred to Al modified SBA-16 supports, and x signified the synthesis temperatures from 25 to 55°C. The synthesis mechanism of SBA-16 exhibiting different morphologies was proposed. Meanwhile, the DBT (500ppm) HDS performance over NiMo/S-50 catalyst exhibited the highest conversion of 95.2% at the WHSV of 20h−1.
      Graphical abstract image

      PubDate: 2016-08-15T02:51:47Z
       
  • Experimental and CFD simulations of fluid flow and temperature
           distribution in a natural circulation driven Passive Moderator Cooling
           System of an advanced nuclear reactor
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Eshita Pal, Mukesh Kumar, Arun K. Nayak, Jyeshtharaj B. Joshi
      The Passive Moderator Cooling System (PMCS) of the Advanced Heavy Water Reactor is designed to remove heat from the moderator passively in case of an extended station black out condition (SBO). The hot heavy-water moderator inside the Calandria rises upward due to buoyancy, cooled in a shell and tube heat exchanger (located within the loop) and returns back to the Calandria, completing a natural circulation loop. The heat exchanger, in turn, is cooled by water from a Gravity Driven Water Pool (GDWP); forming a second loop. This coupled natural circulation loop system provides sufficient cooling to prevent the increase of moderator temperature inside the Calandria vessel beyond safe limits during SBO. The feasibility of such a system should be assessed before it is implemented in the reactor. Thus, a scaled test facility was set up to simulate the thermal hydraulic characteristics of the PMCS. A set of time varying power experiments were performed, which capture the flow initiation from rest phenomena and the multidimensional natural convection flow in a coupled natural circulation system. Next, the experimental geometry was simulated using the three-dimensional computational fluid dynamics code (OpenFoam 2.2.0), which predicted temperature and flow distribution inside the system. The CFD results agree well with the experimental data within ±6%. The flow initiation phenomena shows that the initial flow generated recirculates within the Calandria, after ~900s the flow is able to come out of the Calandria. The experiments show a time lag between the starting of the primary and secondary loop circulation. This work demonstrates the experimental and computational capability to understand and design an effective Passive Moderator Cooling System.


      PubDate: 2016-08-11T04:38:06Z
       
  • CFD-PBM simulation of droplets size distribution in rotor-stator mixing
           devices
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Chengpeng Qin, Chao Chen, Qi Xiao, Ning Yang, Cansheng Yuan, Christian Kunkelmann, Murat Cetinkaya, Kerstin Mülheims
      Rotor-Stator mixing devices (RS) have found widespread application in mixing, dispersion and emulsification processes to acquire the desirable droplet size distribution (DSD) which is critical to the function and quality of products. Thus the precise control of DSD through the rational design and optimization of process or formulation is highly demanded. Computational fluid dynamics (CFD) becomes increasingly important to simulate the complex turbulence flow in RS devices which has significant impact on the final DSD. CFD can also be integrated with population balance equations (PBE) to predict the DSD as long as the droplet breakage and coalescence rates could be accurately modeled by the kernel functions. However, the underlying physics of droplet breakage and coalescence is complex and far from being well understood. We simulated the liquid–liquid two-phase flow and DSD for a weak coalescence emulsification system in a Megatron RS mixer with the CFD-PBM approach, then tentatively proposed a novel approach for correcting the breakage kernels based on the Energy-Minimization Multi-Scale (EMMS) concept. This method features the multi-scale resolution of energy dissipation, and utilizes the so-called meso-scale energy dissipation to derive a correction factor for the breakage rate for PBE. The results show that the new model can greatly improve the CFD-PBM simulation, and the DSD predicted is in good agreement with experiments, demonstrating the rationality and potential of this new approach.


      PubDate: 2016-08-11T04:38:06Z
       
  • Inhibiting effects of transition metal salts on methane hydrate stability
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Traci Y. Sylva, Christopher K. Kinoshita, Stephen M. Masutani
      The behavior of clathrate hydrates in the presence of transition metal salts was investigated using a Differential Scanning Calorimeter (DSC). Specifically, a DSC was employed to determine the onset temperature for methane hydrate decomposition in the presence of ferric chloride hexahydrate, [FeCl2(H2O)4]Cl·2H2O, anhydrous ferric chloride, FeCl3, MnSO4, FeSO4, CuSO4, and AgNO3, and to compare the inhibiting properties of these transition metal salts with NaCl and CaCl2, two well-known salt inhibitors. The degree of methane hydrate inhibition induced by the salts that were studied (as indicated by the reduction in dissociation temperature at a given pressure), when compared between mixtures with the same mole percentages of the salt, increases in the following order: FeSO4≈CuSO4<MnSO4≈AgNO3≈CaCl2<NaCl<FeCl3. A smaller decrease in the dissociation temperature was observed with salts that contained the larger sulfate anion when compared to salts that contained the smaller chloride anion. Smaller decreases in the dissociation temperature were observed with salts that contained smaller cations like Fe2+ when compared to salts that contained larger cations such as Ag+ and Mn2+. It is posited that the interaction between water with salt ions results in hydrate formation inhibition and the strength of the salt ion-dipole bond between the metal ion and water molecules correlates with the degree of inhibition. Consideration of the charge and size characteristics of the anion and cation components of the tested salts appears to explain this behavior.


      PubDate: 2016-08-11T04:38:06Z
       
  • Nucleation curves of methane – propane mixed gas hydrates in
           hydrocarbon oil
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Nobuo Maeda
      The second generation High Pressure Automated Lag Time Apparatus (HP–ALTA MkII) was used to measure the nucleation curves of Structure II (sII)–forming methane–propane mixed gas hydrates on the surface of a quasi–free water droplet suspended in involatile hydrocarbon oil, squalane. The measured nucleation curves were then compared to the previously obtained nucleation curves of the same guest gas hydrate on a quasi–free water droplet supported by perfluorodecalin. The comparison of the two sets of data sets showed that the nucleation rates of the two systems were broadly similar to each other. A simple master nucleation curve was derived for each system as a function of the system subcooling. The model-independent empirical equation that relates the nucleation rate to the system subcooling was J water-guest (s−1 m−2)=2.38×10−39ΔT 26.746 for a quasi-free water droplet suspended in squalane and J water-guest (s−1 m−2)=7.70×10−11ΔT 7.931 for a quasi-free water droplet supported by perfluorodecalin. The nucleation rates predicted by these empirical equations are then compared to the nucleation rates of other relevant systems in the literature. The model-independent analysis method for the derivation of nucleation curves we have developed can be applied to constant cooling ramp data obtained by any experimental techniques.


      PubDate: 2016-08-11T04:38:06Z
       
  • Gas–liquid mass transfer in a falling film microreactor: Effect of
           reactor orientation on liquid-side mass transfer coefficient
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): David Lokhat, Ashveer Krishen Domah, Kuveshan Padayachee, Aman Baboolal, Deresh Ramjugernath
      Microreactors offer a unique platform for chemical syntheses and have been applied to numerous reaction types including nitrations, fluorinations and hydrogenations. A key feature of falling film microreactors is the comparably large specific surface area they afford compared to conventional reactors. The enhanced heat and mass transfer characteristics can be exploited for rapid and exothermic reactions. Adequate understanding of the mass transfer processes occurring within microchannels is necessary for proper reactor design and optimization. In the current study the influence of reaction plate orientation and gas flowrate on liquid-side mass transfer coefficient was investigated via CO2 absorption experiments. Lower plate angles resulted in lower liquid-side mass transfer coefficients. At higher film velocities the rate of mass transfer was greater. The experimentally determined mass transfer coefficients were at least twice as high as those predicted either by film or penetration theory. The enhancement in mass transfer is suggested to be due to cellular convection in the microchannels. For inclined reaction plates, increasing the gas flowrate had a positive effect on the mass transfer characteristics due to induced fluctuations of the gas–liquid interface.
      Graphical abstract image

      PubDate: 2016-08-11T04:38:06Z
       
  • QMOM-based population balance model involving a fractal dimension for the
           flocculation of latex particles
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Mélody Vlieghe, Carole Coufort-Saudejaud, Alain Liné, Christine Frances
      An experimental and computational study of agglomeration and breakage processes for fully destabilized latex particles under turbulent flow conditions in a jar is presented. The particle size distribution (PSD) and the fractal dimension of flocs of latex particles were monitored using an on-line laser diffraction technique. A population balance equation (PBE) was adapted to our problem by including the fractal dimension in its formulation as well as in the aggregation and breakage kernels. The quadrature method of moments was used for the resolution. The adjustment of 4 model parameters was then conducted on the first 6 moments of the PSD for various mean shear rates. The model correctly predicts the evolution of the first 6 moments calculated from the experimental PSD. The experimental results were adequately simulated by a single set of adjusted parameters, proving the relevance of the dependency on the fractal dimension and mean shear rate. A sensitivity analysis was performed on two main adjusted parameters highlighting the major roles of (1) the power to which the mean shear rate is raised in the breakage kernel and (2) the sizes of the colliding aggregates in the collision efficiency model. Finally, analytical relations between the sink and source terms of the breakage or aggregation of the PBE were derived and discussed, highlighting interesting features of the PBE model.


      PubDate: 2016-08-11T04:38:06Z
       
  • Effect of foam processing parameters on bubble nucleation and growth
           dynamics in high-pressure foam injection molding
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Vahid Shaayegan, Guilong Wang, Chul B. Park
      We used an innovative visualization mold to investigate the effect of foam processing parameters on bubble nucleation and growth. This was also done to uncover the mechanisms responsible for cellular structural development in the high-pressure foam injection molding process. The effects of the injection speed, the injection gate geometry, the blowing agent content, the melt flow rate and the use of talc as a heterogeneous nucleating agent on the formation and dynamics of cell bubbles were all explored. In the high-pressure foam injection molding process with a proper packing pressure, the overall cell density did not change with the injection speed nor with the injection gate resistance. However, the cell density increased significantly with the blowing agent's concentration and with a nucleating agent. We also observed the growth mechanism of the bubbles in a confined mold cavity, and concluded that the bubble growth rate decreased as the cell density increased. In addition, the satelliting phenomenon, i.e. bubble nucleation around the previously nucleated cells, was observed. This was due to the induced stress fluctuations in the surrounding melt, which could eventually affect the final cellular structure.


      PubDate: 2016-08-11T04:38:06Z
       
  • Mass transfer, gas hold-up and cell cultivation studies in a bottom
           agitated draft tube reactor and multiple impeller Rushton turbine
           configuration
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Petri Tervasmäki, Marko Latva-Kokko, Sanna Taskila, Juha Tanskanen
      Gas–liquid mass transfer is an important phenomenon in aerobic microbial cultivations, and the mass transfer performance of an industrial reactor strongly affects the overall process economics. Traditionally, industrial and laboratory bioreactors have been agitated with flat disc turbines (Rushton turbines) although there are many variants to this design. In addition, pneumatically agitated reactors such as bubble columns and airlift reactors have been studied and used by the industry. In this study we utilize an agitated draft tube reactor in cell cultivation and mass transfer studies. A standard reactor geometry agitated with three Rushton turbines was compared to Outotec OKTOP®9000 reactor which is a draft tube reactor agitated with a single impeller located just below the draft tube. The experiments included cell cultivation with Pichia pastoris yeast, determination of overall mass transfer coefficient by dynamic gassing in method and measurement of local gas hold-up by electrical impedance tomography (EIT). In addition, agitation power was estimated from the power consumption of the DC-motor. OKTOP®9000 reactor was found to have higher k L a values than the STR with similar agitation power and gas flowrate. The overall gas hold-up was similar in both geometries at same power inputs and gas flow rates. However, some significant differences were detected in the distribution of gas phase between the two geometries especially in the axial direction. Also changes in the gas dispersion regime can be detected from the spatial distribution of the gas hold-up measured by EIT. The cell cultivation experiments showed the applicability of this type of agitated draft tube reactor to bioprocesses although a direct comparison with Rushton geometry is not straightforward.
      Graphical abstract image

      PubDate: 2016-08-11T04:38:06Z
       
  • Stability analysis of stratified Rayleigh–Bénard–Poiseuille
           convection. Part II: Influence of thermocapillary forces
    • Abstract: Publication date: 22 November 2016
      Source:Chemical Engineering Science, Volume 155
      Author(s): Éliton Fontana, Erasmo Mancusi, Antônio A.U. de Souza, Selene M.A.G.U. de Souza
      The development of convective cells in horizontal stratified systems can be induced by buoyancy or thermocapillary forces (Marangoni effect). When both mechanisms of instability are present it is expected a non-trivial influence of one over the other, with the main characteristics based primarily on the ratio between the buoyancy forces acting in each layer. In this study, linear stability analysis is used to investigate the influence of the thermocapillary effect in double layer stratified systems confined between two solid walls and heated from below, including cases where a pressure gradient induces fluid flow parallel to the walls. To simplify the analysis, it is assumed that the fluids in both layers have similar properties and the interface deformation is neglected. The presence of thermocapillary forces acting on the interface generates a complex behavior, particularly when the upper layer is deeper than the lower layer, which causes the convective cells to emerge initially in the upper layer. In this case, oscillatory states can appear as a result of the competition between the mechanisms of instability. This behavior is not observed if the thermocapillary forces are neglected; therefore, in order to obtain a complete picture of the system stability, it is important to include the Marangoni effect. The increases in the Reynolds and Prandtl numbers showed a similar effect. For low Re or Pr values, the thermocapillary forces initially stabilize the system, however, after a certain threshold the increase in the Marangoni number tends to destabilize the system. The presence of parallel flow also hinders the formation of oscillatory states. When the convective cells emerge initially on the lower layer, the increase in the Marangoni number facilitates the development of the cells, since the thermocapillary forces always act in the same direction as the buoyancy forces at the interface.


      PubDate: 2016-08-11T04:38:06Z
       
 
 
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